Deus Ex Machina

A plot device in which a difficult problem is resolved by the introduction of a new character, ability, or item. The technique has been found in literature as far back as the ancient Greek tragedies, frequently being utilized by Euripides to tie up his stories. In general, deus ex machina is considered to be a sign of poor storytelling, as external resolution undermines the fundamental logic of a story--why depict any conflict at all if a hand will be waved and all characters emerge unscathed?

Deus ex machina occurs across genres and examples include: the appearance of Gil Krundle in Beerfest; the last-minute royal decree that saves Mack the Knife in The Threepenny Opera; any time a Dragonball Z character discovers a new power level (Super Saiyan 1, 2, etc.) to help them defeat a villain.